Pediatric overweight has reached epidemic levels and, at 36%, children with autism spectrum disorder (ASD) have a higher rate of overweight than typically developing children. Pediatric overweight is a major health problem because it is linked to childhood onset of dyslipidemia, hypertension, high blood sugar, and Type 2 Diabetes. Also youths who grow up overweight, will as adults, face higher rates of hypertension, heart disease, atherosclerosis, colorectal cancer, arthritis, and chronic overweight. Yet, despite a pressing need for effective prevention and intervention efforts for overweight in children with ASD, we are significantly hampered in developing appropriate programs because we lack empirical data on potentially important dietary and behavioral factors. Children with ASD have unique impairments and behaviors that can complicate weight management, including difficulty with motor skills, cognitive difficulties, problematic mealtime behaviors and greater food refusal and selectivity than typically developing children, which make it highly unlikely that available weight management interventions for typically developing children will generalize to them. Therefore, there is a critical need for research examining factors related to overweight in children with ASD specifically. The long-term goal of our research is to identify evidence-based methods for preventing and treating overweight in children with ASD. The goal of the current project is to identify parent and child mealtime behavior and diet characteristics that are related to child weight status as a basis for future research to develop a suitable weight management program for children with ASD. The current study aims are: 1) identify child and parent mealtime behaviors associated with present and future weight in young children with ASD and 2) assess if diet variables are related to present and future child weight. This project is significant because t is expected to provide much needed information on factors related to overweight in children with ASD, which can be used to develop and refine weight management programs for children with ASD, an understudied population for weight management. The project is innovative because of its proposed home-based ethnographic methodology and longitudinal design, which both represent a substantial departure from existing studies in children with ASD and offer the opportunity to collect data necessary for intervention development. We expect our approach will greatly expand the body of knowledge for this under-studied but vulnerable population of children and will lay the groundwork for the development and dissemination of tailored weight management programs, two research goals which are in line with priorities for the NIH Autism Interagency Coordinating Center and the Autism Treatment Networks. Given the large number of children with ASD and the high prevalence of overweight in this population, the development and dissemination of tailored weight management programs for these children is expected to lead to improved health and functioning for a large number of children.